Navigation

Pithos API

Introduction

Pithos is a storage service implemented by GRNET (http://www.grnet.gr). Data is stored as objects, organized in containers, belonging to an account. This hierarchy of storage layers has been inspired by the OpenStack Object Storage (OOS) API and similar CloudFiles API by Rackspace. The Pithos API follows the OOS API as closely as possible. One of the design requirements has been to be able to use Pithos with clients built for the OOS, without changes.

However, to be able to take full advantage of the Pithos infrastructure, client software should be aware of the extensions that differentiate Pithos from OOS. Pithos objects can be updated, or appended to. Pithos will store sharing permissions per object and enforce corresponding authorization policies. Automatic version management, allows taking account and container listings back in time, as well as reading previous instances of objects.

The storage backend of Pithos is block oriented, permitting efficient, deduplicated data placement. The block structure of objects is exposed at the API layer, in order to encourage external software to implement advanced data management operations.

This document’s goals are:

  • Define the Pithos ReST API that allows the storage and retrieval of data and metadata via HTTP calls
  • Specify metadata semantics and user interface guidelines for a common experience across client software implementations

The present document is meant to be read alongside the OOS API documentation. Thus, it is suggested that the reader is familiar with associated technologies, the OOS API as well as the first version of the Pithos API. This document refers to the second version of Pithos. Information on the first version of the storage API can be found at http://code.google.com/p/gss.

Whatever marked as to be determined (TBD), should not be considered by implementors.

More info about Pithos can be found here: https://code.grnet.gr/projects/pithos

Document Revisions

Revision Description
0.13 (Mar 27, 2013) Restrict public object listing only to the owner. Do not propagate public URL information in shared objects.
0.13 (Jan 21, 2013) Proxy identity management services
UUID to displayname translation
0.9 (Feb 17, 2012) Change permissions model.
0.10 (Jul 18, 2012) Support for bulk COPY/MOVE/DELETE
Optionally include public objects in listings.
0.9 (Feb 17, 2012) Change permissions model.
Do not include user-defined metadata in account/container/object listings.
0.8 (Jan 24, 2012) Update allowed versioning values.
Change policy/meta formatting in JSON/XML replies.
Document that all non-ASCII characters in headers should be URL-encoded.
Support metadata-based queries when listing objects at the container level.
Note Content-Type issue when using the internal django web server.
Add object UUID field.
Always reply with the MD5 in the ETag.
Note that /login will only work if an external authentication system is defined.
Include option to ignore Content-Type on COPY/MOVE.
Use format parameter for conflict (409) and uploaded hash list (container level) replies.
0.7 (Nov 21, 2011) Suggest upload/download methods using hashmaps.
Propose syncing algorithm.
Support cross-account object copy and move.
Pass token as a request parameter when using POST via an HTML form.
Optionally use source account to update object from another object.
Use container POST to upload missing blocks of data.
Report policy in account headers.
Add insufficient quota reply.
Use special meta to always report Merkle hash.
0.6 (Sept 13, 2011) Reply with Merkle hash as the ETag when updating objects.
Include version id in object replace/change replies.
Change conflict (409) replies format to text.
Tags should be migrated to a meta value.
Container PUT updates metadata/policy.
Report allowed actions in shared object replies.
Provide https://hostname/login for Shibboleth authentication.
Use hashmap parameter in object GET/PUT to use hashmaps.
0.5 (July 22, 2011) Object update from another object’s data.
Support object truncate.
Create object using a standard HTML form.
Purge container/object history.
List other accounts that share objects with a user.
List shared containers/objects.
Update implementation guidelines.
Check preconditions when creating/updating objects.
0.4 (July 01, 2011) Object permissions and account groups.
Control versioning behavior and container quotas with container policy directives.
Support updating/deleting individual metadata with POST.
Create object using hashmap.
0.3 (June 14, 2011) Large object support with X-Object-Manifest.
Allow for publicly available objects via https://hostname/public.
Support time-variant account/container listings.
Add source version when duplicating with PUT/COPY.
Request version in object HEAD/GET requests (list versions with GET).
0.2 (May 31, 2011) Add object meta listing and filtering in containers.
Include underlying storage characteristics in container meta.
Support for partial object updates through POST.
Expose object hashmaps through GET.
Support for multi-range object GET requests.
0.1 (May 17, 2011) Initial release. Based on OpenStack Object Storage Developer Guide API v1 (Apr. 15, 2011).

Pithos Users and Authentication

In Pithos, each user is uniquely identified by a token. All API requests require a token and each token is internally resolved to an account string. The API uses the account string to identify the user’s own files, thus whether a request is local or cross-account.

Pithos does not keep a user database. For development and testing purposes, user identifiers and their corresponding tokens can be defined in the settings file. However, Pithos is designed with an external authentication service in mind. This service must handle the details of validating user credentials and communicate with Pithos via a middleware software component that, given a token, fills in the internal request account variable.

Client software using Pithos, if not already knowing a user’s identifier and token, should forward to the /login URI. The Pithos server, depending on its configuration will redirect to the appropriate login page.

The login URI accepts the following parameters:

Request Parameter Name Value
next The URI to redirect to when the process is finished
renew Force token renewal (no value parameter)
force Force logout current user (no value parameter)

When done with logging in, the service’s login URI should redirect to the URI provided with next, adding user and token parameters, which contain the account and token fields respectively.

A user management service that implements a login URI according to these conventions is Astakos (https://code.grnet.gr/projects/astakos), by GRNET.

User feedback

Client software using Pithos, should forward to the /feedback URI. The Pithos service, depending on its configuration will delegate the request to the appropriate identity management URI.

Uri Method Description
/pithos/astakos/feedback POST Send feedback

Request Parameter Name Value
feedback_msg Feedback message
feedback_data Additional information about service client status

Request Header Name Value
X-Auth-Token User authentication token

Return Code Description
200 (OK) The request succeeded
502 (Bad Gateway) Send feedback failure
400 (Bad Request) Method not allowed or invalid message data
401 (Unauthorized) Missing or expired user token
500 (Internal Server Error) The request cannot be completed because of an internal error

User translation catalogs

Client software using Pithos, should forward to the /user_catalogs URI to get uuid to displayname translations and vice versa. The Pithos service, depending on its configuration will delegate the request to the appropriate identity management URI.

Uri Method Description
/pithos/astakos/user_catalogs POST Get 2 catalogs containing uuid to displayname mapping and the opposite

Request Header Name Value
X-Auth-Token User authentication token

The request body is a json formatted dictionary containing a list with uuids and another list of displaynames to translate.

Example request content:

{"displaynames": ["user1@example.com", "user2@example.com"],
 "uuids":["ff53baa9-c025-4d56-a6e3-963db0438830", "a9dc21d2-bcb2-4104-9a9e-402b7c70d6d8"]}

Example reply:

{"displayname_catalog": {"user1@example.com": "a9dc21d2-bcb2-4104-9a9e-402b7c70d6d8",
                      "user2@example.com": "816351c7-7405-4f26-a968-6380cf47ba1f"},
'uuid_catalog': {"a9dc21d2-bcb2-4104-9a9e-402b7c70d6d8": "user1@example.com",
                 "ff53baa9-c025-4d56-a6e3-963db0438830": "user2@example.com"}}

Return Code Description
200 (OK) The request succeeded
400 (Bad Request) Method not allowed or request body is not json formatted
401 (Unauthorized) Missing or expired or invalid user token
500 (Internal Server Error) The request cannot be completed because of an internal error

The Pithos API

The URI requests supported by the Pithos API follow one of the following forms:

  • Top level: https://hostname/v1/
  • Account level: https://hostname/v1/<account>
  • Container level: https://hostname/v1/<account>/<container>
  • Object level: https://hostname/v1/<account>/<container>/<object>

All requests must include an X-Auth-Token - as a header, or a parameter.

The allowable request operations and respective return codes per level are presented in the remainder of this chapter. Common to all requests are the following return codes.

Return Code Description
400 (Bad Request) The request is invalid
401 (Unauthorized) Missing or invalid token
403 (Forbidden) Request not allowed
404 (Not Found) The requested resource was not found
413 (Request Entity Too Large) Insufficient quota to complete the request
503 (Service Unavailable) The request cannot be completed because of an internal error

Top Level

List of operations:

Operation Description
GET Authentication (for compatibility with the OOS API) or list allowed accounts

GET

If the X-Auth-User and X-Auth-Key headers are given, a dummy X-Auth-Token and X-Storage-Url will be replied, which can be used as a guest token/namespace for testing Pithos.

Return Code Description
204 (No Content) The request succeeded

If an X-Auth-Token is already present, the operation will be interpreted as a request to list other accounts that share objects to the user.

Request Parameter Name Value
limit The amount of results requested (default is 10000)
marker Return containers with name lexicographically after marker
format Optional extended reply type (can be json or xml)

The reply is a list of account names. If a format=xml or format=json argument is given, extended information on the accounts will be returned, serialized in the chosen format. For each account, the information will include the following (names will be in lower case and with hyphens replaced with underscores):

Name Description
name The name of the account
last_modified The last account modification date (regardless of until)

Example format=json reply:

[{"name": "user-uuid", "last_modified": "2011-12-02T08:10:41.565891+00:00"}, ...]

Example format=xml reply:

<?xml version="1.0" encoding="UTF-8"?>
<accounts>
  <account>
    <name>user-uuid</name>
    <last_modified>2011-12-02T08:10:41.565891+00:00</last_modified>
  </account>
  <account>...</account>
</accounts>
Return Code Description
200 (OK) The request succeeded
204 (No Content) The user has no access to other accounts (only for non-extended replies)

Will use a 200 return code if the reply is of type JSON/XML.

Account Level

List of operations:

Operation Description
HEAD Retrieve account metadata
GET List containers
POST Update account metadata

GET

Request Header Name Value
If-Modified-Since Retrieve if account has changed since provided timestamp
If-Unmodified-Since Retrieve if account has not changed since provided timestamp

Request Parameter Name Value
limit The amount of results requested (default is 10000)
marker Return containers with name lexicographically after marker
format Optional extended reply type (can be json or xml)
shared Show only shared containers (no value parameter)
public Show only public containers (no value parameter / avalaible only for owner requests)
until Optional timestamp

The reply is a list of container names. Account headers (as in a HEAD request) will also be included. Cross-user requests are not allowed to use until and only include the account/container modification dates in the reply.

If a format=xml or format=json argument is given, extended information on the containers will be returned, serialized in the chosen format. For each container, the information will include all container metadata, except user-defined (names will be in lower case and with hyphens replaced with underscores):

Name Description
name The name of the container
count The number of objects inside the container
bytes The total size of the objects inside the container
last_modified The last container modification date (regardless of until)
x_container_until_timestamp The last container modification date until the timestamp provided
x_container_policy Container behavior and limits

Example format=json reply:

[{"name": "pithos",
  "bytes": 62452,
  "count": 8374,
  "last_modified": "2011-12-02T08:10:41.565891+00:00",
  "x_container_policy": {"quota": "53687091200", "versioning": "auto"}}, ...]

Example format=xml reply:

<?xml version="1.0" encoding="UTF-8"?>
<account name="user-uuid">
  <container>
    <name>pithos</name>
    <bytes>62452</bytes>
    <count>8374</count>
    <last_modified>2011-12-02T08:10:41.565891+00:00</last_modified>
    <x_container_policy>
      <key>quota</key><value>53687091200</value>
      <key>versioning</key><value>auto</value>
    </x_container_policy>
  </container>
  <container>...</container>
</account>

For more examples of container details returned in JSON/XML formats refer to the OOS API documentation. In addition to the OOS API, Pithos returns policy fields, grouped as key-value pairs.

Return Code Description
200 (OK) The request succeeded
204 (No Content) The account has no containers (only for non-extended replies)
304 (Not Modified) The account has not been modified
412 (Precondition Failed) The condition set can not be satisfied

Will use a 200 return code if the reply is of type JSON/XML.

POST

Request Header Name Value
X-Account-Group-* Optional user defined groups
X-Account-Meta-* Optional user defined metadata

Request Parameter Name Value
update Do not replace metadata/groups (no value parameter)

No reply content/headers.

The operation will overwrite all user defined metadata, except if update is defined. To create a group, include an X-Account-Group-* header with the name in the key and a comma separated list of user identifiers in the value. If no X-Account-Group-* header is present, no changes will be applied to groups. The update parameter also applies to groups. To delete a specific group, use update and an empty header value.

Return Code Description
202 (Accepted) The request has been accepted

Container Level

List of operations:

Operation Description
HEAD Retrieve container metadata
GET List objects
PUT Create/update container
POST Update container metadata
DELETE Delete container

HEAD

Request Header Name Value
If-Modified-Since Retrieve if container has changed since provided timestamp
If-Unmodified-Since Retrieve if container has not changed since provided timestamp

Request Parameter Name Value
until Optional timestamp

Cross-user requests are not allowed to use until and only include the container modification date in the reply.

Reply Header Name Value
X-Container-Object-Count The total number of objects in the container
X-Container-Bytes-Used The total number of bytes of all objects stored
X-Container-Block-Size The block size used by the storage backend
X-Container-Block-Hash The hash algorithm used for block identifiers in object hashmaps
X-Container-Until-Timestamp The last container modification date until the timestamp provided
X-Container-Object-Meta A list with all meta keys used by objects (TBD)
X-Container-Policy-* Container behavior and limits
X-Container-Meta-* Optional user defined metadata
Last-Modified The last container modification date (regardless of until)

The keys returned in X-Container-Object-Meta are all the unique strings after the X-Object-Meta- prefix, formatted as a comma-separated list. See container PUT for a reference of policy directives. (TBD)

Return Code Description
204 (No Content) The request succeeded

GET

Request Header Name Value
If-Modified-Since Retrieve if container has changed since provided timestamp
If-Unmodified-Since Retrieve if container has not changed since provided timestamp

Request Parameter Name Value
limit The amount of results requested (default is 10000)
marker Return containers with name lexicographically after marker
prefix Return objects starting with prefix
delimiter Return objects up to the delimiter (discussion follows)
path Assume prefix=path and delimiter=/
format Optional extended reply type (can be json or xml)
meta Return objects that satisfy the key queries in the specified comma separated list (use <key>, !<key> for existence queries, <key><op><value> for value queries, where <op> can be one of =, !=, <=, >=, <, >)
shared Show only objects (no value parameter)
public Show only public objects (no value parameter / avalaible only for owner reqeusts)
until Optional timestamp

The path parameter overrides prefix and delimiter. When using path, results will include objects ending in delimiter.

The keys given with meta will be matched with the strings after the X-Object-Meta- prefix.

The reply is a list of object names. Container headers (as in a HEAD request) will also be included. Cross-user requests are not allowed to use until and include the following limited set of headers in the reply:

Reply Header Name Value
X-Container-Block-Size The block size used by the storage backend
X-Container-Block-Hash The hash algorithm used for block identifiers in object hashmaps
X-Container-Object-Meta A list with all meta keys used by allowed objects (TBD)
Last-Modified The last container modification date

If a format=xml or format=json argument is given, extended information on the objects will be returned, serialized in the chosen format. For each object, the information will include all object metadata, except user-defined (names will be in lower case and with hyphens replaced with underscores). User-defined metadata includes X-Object-Meta-*, X-Object-Manifest, Content-Disposition and Content-Encoding keys. Also, sharing directives will only be included with the actual shared objects (inherited permissions are not calculated):

Name Description
name The name of the object
hash The ETag of the object
bytes The size of the object
content_type The MIME content type of the object
last_modified The last object modification date (regardless of version)
x_object_hash The Merkle hash
x_object_uuid The object’s UUID
x_object_version The object’s version identifier
x_object_version_timestamp The object’s version timestamp
x_object_modified_by The user that committed the object’s version
x_object_sharing Object permissions (optional)
x_object_allowed_to Allowed actions on object (optional)
x_object_public Object’s publicly accessible URI (optional: present if the object is public and the request user is the object owner)

Sharing metadata and last modification timestamp will only be returned if there is no until parameter defined.

Extended replies may also include virtual directory markers in separate sections of the json or xml results. Virtual directory markers are only included when delimiter is explicitly set. They correspond to the substrings up to and including the first occurrence of the delimiter. In JSON results they appear as dictionaries with only a subdir key. In XML results they appear interleaved with <object> tags as <subdir name="..." />. In case there is an object with the same name as a virtual directory marker, the object will be returned.

Example format=json reply:

[{"name": "object",
  "bytes": 0,
  "hash": "d41d8cd98f00b204e9800998ecf8427e",
  "content_type": "application/octet-stream",
  "last_modified": "2011-12-02T08:10:41.565891+00:00",
  "x_object_hash": "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855",
  "x_object_uuid": "8ed9af1b-c948-4bb6-82b0-48344f5c822c",
  "x_object_version": 98,
  "x_object_version_timestamp": "1322813441.565891",
  "x_object_modified_by": "user-uuid"}, ...]

Example format=xml reply:

<?xml version="1.0" encoding="UTF-8"?>
<container name="pithos">
  <object>
    <name>object</name>
    <bytes>0</bytes>
    <hash>d41d8cd98f00b204e9800998ecf8427e</hash>
    <content_type>application/octet-stream</content_type>
    <last_modified>2011-12-02T08:10:41.565891+00:00</last_modified>
    <x_object_hash>e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855</x_object_hash>
    <x_object_uuid>8ed9af1b-c948-4bb6-82b0-48344f5c822c</x_object_uuid>
    <x_object_version>98</x_object_version>
    <x_object_version_timestamp>1322813441.565891</x_object_version_timestamp>
    <x_object_modified_by>user-uuid</x_object_modified_by>
  </object>
  <object>...</object>
</container>

For more examples of container details returned in JSON/XML formats refer to the OOS API documentation. In addition to the OOS API, Pithos returns more fields that should help with synchronization.

Return Code Description
200 (OK) The request succeeded
204 (No Content) The account has no containers (only for non-extended replies)
304 (Not Modified) The container has not been modified
412 (Precondition Failed) The condition set can not be satisfied

Will use a 200 return code if the reply is of type JSON/XML.

PUT

Request Header Name Value
X-Container-Policy-* Container behavior and limits
X-Container-Meta-* Optional user defined metadata

No reply content/headers.

If no policy is defined, the container will be created with the default values. Available policy directives:

  • versioning: Set to auto or none (default is auto)
  • quota: Size limit in KB (default is 0 - unlimited)

If the container already exists, the operation is equal to a POST with update defined.

Return Code Description
201 (Created) The container has been created
202 (Accepted) The request has been accepted

POST

Request Header Name Value
Content-Length The size of the supplied data (optional, to upload)
Content-Type The MIME content type of the supplied data (optional, to upload)
Transfer-Encoding Set to chunked to specify incremental uploading (if used, Content-Length is ignored)
X-Container-Policy-* Container behavior and limits
X-Container-Meta-* Optional user defined metadata

Request Parameter Name Value
format Optional hash list reply type (can be json or xml)
update Do not replace metadata/policy (no value parameter)

No reply content/headers, except when uploading data, where the reply consists of a list of hashes for the blocks received (in the format specified).

The operation will overwrite all user defined metadata, except if update is defined. To change policy, include an X-Container-Policy-* header with the name in the key. If no X-Container-Policy-* header is present, no changes will be applied to policy. The update parameter also applies to policy - deleted values will revert to defaults. To delete/revert a specific policy directive, use update and an empty header value. See container PUT for a reference of policy directives.

To upload blocks of data to the container, set Content-Type to application/octet-stream and Content-Length to a valid value (except if using chunked as the Transfer-Encoding).

Return Code Description
202 (Accepted) The request has been accepted

DELETE

Request Parameter Name Value
until Optional timestamp
delimiter Optional delete objects starting with container name and delimiter

If until is defined, the container is “purged” up to that time (the history of all objects up to then is deleted). If also delimiter is defined, purge is applied only on the container.

No reply content/headers.

Return Code Description
204 (No Content) The request succeeded
409 (Conflict) The container is not empty

Object Level

List of operations:

Operation Description
HEAD Retrieve object metadata
GET Read object data
PUT Write object data or copy/move object
COPY Copy object
MOVE Move object
POST Update object metadata/data
DELETE Delete object

HEAD

Request Header Name Value
If-Match Retrieve if ETags match
If-None-Match Retrieve if ETags don’t match
If-Modified-Since Retrieve if object has changed since provided timestamp
If-Unmodified-Since Retrieve if object has not changed since provided timestamp

Request Parameter Name Value
version Optional version identifier

Reply Header Name Value
ETag The ETag of the object
Content-Length The size of the object
Content-Type The MIME content type of the object
Last-Modified The last object modification date (regardless of version)
Content-Encoding The encoding of the object (optional)
Content-Disposition The presentation style of the object (optional)
X-Object-Hash The Merkle hash
X-Object-UUID The object’s UUID
X-Object-Version The object’s version identifier
X-Object-Version-Timestamp The object’s version timestamp
X-Object-Modified-By The user that comitted the object’s version
X-Object-Manifest Object parts prefix in <container>/<object> form (optional)
X-Object-Sharing Object permissions (optional)
X-Object-Shared-By Object inheriting permissions (optional)
X-Object-Allowed-To Allowed actions on object (optional)
X-Object-Public Object’s publicly accessible URI (optional: present if the object is public and the request user is the object owner)
X-Object-Meta-* Optional user defined metadata

Return Code Description
200 (No Content) The request succeeded

GET

Request Header Name Value
Range Optional range of data to retrieve
If-Range Retrieve the missing part if entity is unchanged; otherwise, retrieve the entire new entity (used together with Range header)
If-Match Retrieve if ETags match
If-None-Match Retrieve if ETags don’t match
If-Modified-Since Retrieve if object has changed since provided timestamp
If-Unmodified-Since Retrieve if object has not changed since provided timestamp

Request Parameter Name Value
format Optional extended reply type (can be json or xml)
hashmap Optional request for hashmap (no value parameter)
version Optional version identifier or list (specify a format if requesting a list)

The reply is the object’s data (or part of it), except if a hashmap is requested with hashmap, or a version list with version=list (in both cases an extended reply format must be specified). Object headers (as in a HEAD request) are always included.

Hashmaps expose the underlying storage format of the object. Note that each hash is computed after trimming trailing null bytes of the corresponding block. The X-Object-Hash header reports the single Merkle hash of the object’s hashmap (refer to http://bittorrent.org/beps/bep_0030.html for more information).

Example format=json reply:

{"block_hash": "sha1", "hashes": ["7295c41da03d7f916440b98e32c4a2a39351546c", ...], "block_size": 131072, "bytes": 242}

Example format=xml reply:

<?xml version="1.0" encoding="UTF-8"?>
<object name="file" bytes="24223726" block_size="131072" block_hash="sha1">
  <hash>7295c41da03d7f916440b98e32c4a2a39351546c</hash>
  <hash>...</hash>
</object>

Version lists include the version identifier and timestamp for each available object version. Version identifiers can be arbitrary strings, so use the timestamp to find newer versions.

Example format=json reply:

{"versions": [[85, "1322734861.248469"], [86, "1322734905.009272"], ...]}

Example format=xml reply:

<?xml version="1.0" encoding="UTF-8"?>
<object name="file">
  <version timestamp="1322734861.248469">85</version>
  <version timestamp="1322734905.009272">86</version>
  <version timestamp="...">...</version>
</object>

The Range header may include multiple ranges, as outlined in RFC2616. Then the Content-Type of the reply will be multipart/byteranges and each part will include a Content-Range header.

Reply Header Name Value
ETag The ETag of the object
Content-Length The size of the data returned
Content-Type The MIME content type of the object
Content-Range The range of data included (only on a single range request)
Last-Modified The last object modification date (regardless of version)
Content-Encoding The encoding of the object (optional)
Content-Disposition The presentation style of the object (optional)
X-Object-Hash The Merkle hash
X-Object-UUID The object’s UUID
X-Object-Version The object’s version identifier
X-Object-Version-Timestamp The object’s version timestamp
X-Object-Modified-By The user that comitted the object’s version
X-Object-Manifest Object parts prefix in <container>/<object> form (optional)
X-Object-Sharing Object permissions (optional)
X-Object-Shared-By Object inheriting permissions (optional)
X-Object-Allowed-To Allowed actions on object (optional)
X-Object-Public Object’s publicly accessible URI (optional: present if the object is public and the request user is the object owner)
X-Object-Meta-* Optional user defined metadata

Sharing headers (X-Object-Sharing, X-Object-Shared-By and X-Object-Allowed-To) are only included if the request is for the object’s latest version (no specific version parameter is set).

Return Code Description
200 (OK) The request succeeded
206 (Partial Content) The range request succeeded
304 (Not Modified) The object has not been modified
412 (Precondition Failed) The condition set can not be satisfied
416 (Range Not Satisfiable) The requested range is out of limits

PUT

Request Header Name Value
If-Match Put if ETags match with current object
If-None-Match Put if ETags don’t match with current object
ETag The MD5 hash of the object (optional to check written data)
Content-Length The size of the data written
Content-Type The MIME content type of the object
Transfer-Encoding Set to chunked to specify incremental uploading (if used, Content-Length is ignored)
X-Copy-From The source path in the form /<container>/<object>
X-Move-From The source path in the form /<container>/<object>
X-Source-Account The source account to copy/move from
X-Source-Version The source version to copy from
Content-Encoding The encoding of the object (optional)
Content-Disposition The presentation style of the object (optional)
X-Object-Manifest Object parts prefix in <container>/<object> form (optional)
X-Object-Sharing Object permissions (optional)
X-Object-Public Object is publicly accessible (optional)
X-Object-Meta-* Optional user defined metadata

Request Parameter Name Value
format Optional extended request/conflict response type (can be json or xml)
hashmap Optional hashmap provided instead of data (no value parameter)
delimiter Optional copy/move objects starting with object’s path and delimiter (to be used with X-Copy-From/X-Move-From)

The request is the object’s data (or part of it), except if a hashmap is provided (using hashmap and format parameters). If using a hashmap and all different parts are stored in the server, the object is created. Otherwise the server returns Conflict (409) with the list of the missing parts (in simple text format, with one hash per line, or in JSON/XML - depending on the format parameter).

Hashmaps should be formatted as outlined in GET.

Reply Header Name Value
ETag The MD5 hash of the object
X-Object-Version The object’s new version

The X-Object-Sharing header may include either a read=... comma-separated user/group list, or a write=... comma-separated user/group list, or both separated by a semicolon (;). Groups are specified as <account>:<group>. To publish the object, set X-Object-Public to true. To unpublish, set to false, or use an empty header value.

Return Code Description
201 (Created) The object has been created
409 (Conflict) The object can not be created from the provided hashmap (a list of missing hashes will be included in the reply)
411 (Length Required) Missing Content-Length or Content-Type in the request
413 (Request Entity Too Large) Insufficient quota to complete the request
422 (Unprocessable Entity) The MD5 checksum of the data written to the storage system does not match the (optionally) supplied ETag value

COPY

Request Header Name Value
If-Match Proceed if ETags match with object
If-None-Match Proceed if ETags don’t match with object
Destination The destination path in the form /<container>/<object>
Destination-Account The destination account to copy to
Content-Type The MIME content type of the object (optional *)
Content-Encoding The encoding of the object (optional)
Content-Disposition The presentation style of the object (optional)
X-Source-Version The source version to copy from
X-Object-Manifest Object parts prefix in <container>/<object> form (optional)
X-Object-Sharing Object permissions (optional)
X-Object-Public Object is publicly accessible (optional)
X-Object-Meta-* Optional user defined metadata

* When using django locally with the supplied web server, use the ignore_content_type parameter, or do provide a valid Content-Type, as a type of text/plain is applied by default to all requests. Client software should always state ignore_content_type, except when a Content-Type is explicitly defined by the user.

Request Parameter Name Value
format Optional conflict response type (can be json or xml)
ignore_content_type Ignore the supplied Content-Type
delimiter Optional copy objects starting with object’s path and delimiter

Refer to PUT/POST for a description of request headers. Metadata is also copied, updated with any values defined. Sharing/publishing options are not copied.

Reply Header Name Value
X-Object-Version The object’s new version

Return Code Description
201 (Created) The object has been created
413 (Request Entity Too Large) Insufficient quota to complete the request

MOVE

Same as COPY, without the X-Source-Version request header. The MOVE operation is always applied on the latest version.

POST

Request Header Name Value
If-Match Proceed if ETags match with object
If-None-Match Proceed if ETags don’t match with object
Content-Length The size of the data written (optional, to update)
Content-Type The MIME content type of the object (optional, to update)
Content-Range The range of data supplied (optional, to update)
Transfer-Encoding Set to chunked to specify incremental uploading (if used, Content-Length is ignored)
Content-Encoding The encoding of the object (optional)
Content-Disposition The presentation style of the object (optional)
X-Source-Object Update with data from the object at path /<container>/<object> (optional, to update)
X-Source-Account The source account to update from
X-Source-Version The source version to update from (optional, to update)
X-Object-Bytes The updated object’s final size (optional, when updating)
X-Object-Manifest Object parts prefix in <container>/<object> form (optional)
X-Object-Sharing Object permissions (optional)
X-Object-Public Object is publicly accessible (optional)
X-Object-Meta-* Optional user defined metadata

Request Parameter Name Value
format Optional conflict response type (can be json or xml)
update Do not replace metadata (no value parameter)

The Content-Encoding, Content-Disposition, X-Object-Manifest and X-Object-Meta-* headers are considered to be user defined metadata. An operation without the update parameter will overwrite all previous values and remove any keys not supplied. When using update any metadata with an empty value will be deleted.

To change permissions, include an X-Object-Sharing header (as defined in PUT). To publish, include an X-Object-Public header, with a value of true. If no such headers are defined, no changes will be applied to sharing/public. Use empty values to remove permissions/unpublish (unpublishing also works with false as a header value). Sharing options are applied to the object - not its versions.

To update an object’s data:

  • Either set Content-Type to application/octet-stream, or provide an object with X-Source-Object. If Content-Type has some other value, it will be ignored and only the metadata will be updated.
  • If the data is supplied in the request (using Content-Type instead of X-Source-Object), a valid Content-Length header is required - except if using chunked transfers (set Transfer-Encoding to chunked).
  • Set Content-Range as specified in RFC2616, with the following differences:
    • Client software MAY omit last-byte-pos of if the length of the range being transferred is unknown or difficult to determine.
    • Client software SHOULD not specify the instance-length (use a *), unless there is a reason for performing a size check at the server.
  • If Content-Range used has a byte-range-resp-spec = *, data will be appended to the object.

Optionally, truncate the updated object to the desired length with the X-Object-Bytes header.

A data update will trigger an ETag change. Updated ETags may happen asynchronously and appear at the server with a delay.

No reply content. No reply headers if only metadata is updated.

Reply Header Name Value
ETag The new ETag of the object (data updated)
X-Object-Version The object’s new version

Return Code Description
202 (Accepted) The request has been accepted (not a data update)
204 (No Content) The request succeeded (data updated)
411 (Length Required) Missing Content-Length in the request
413 (Request Entity Too Large) Insufficient quota to complete the request
416 (Range Not Satisfiable) The supplied range is invalid

The POST method can also be used for creating an object via a standard HTML form. If the request Content-Type is multipart/form-data, none of the above headers will be processed. The form should have an X-Object-Data field, as in the following example. The token is passed as a request parameter.

<form method="post" action="https://storage.example.synnefo.org/pithos/object-store/v1.0/user-uuid/folder/EXAMPLE.txt?X-Auth-Token=0000" enctype="multipart/form-data">
  <input type="file" name="X-Object-Data">
  <input type="submit">
</form>

This will create/override the object with the given name, as if using PUT. The Content-Type of the object will be set to the value of the corresponding header sent in the part of the request containing the data (usually, automatically handled by the browser). Metadata, sharing and other object attributes can not be set this way. The response will contain the object’s ETag.

Reply Header Name Value
ETag The MD5 hash of the object
X-Object-Version The object’s new version

Return Code Description
201 (Created) The object has been created
413 (Request Entity Too Large) Insufficient quota to complete the request

DELETE

Request Parameter Name Value
until Optional timestamp
delimiter Optional delete also objects starting with object’s path and delimiter

If until is defined, the object is “purged” up to that time (the history up to then is deleted). If also delimiter is defined, purge is applied only on the object.

No reply content/headers.

Return Code Description
204 (No Content) The request succeeded

Sharing and Public Objects

Read and write control in Pithos is managed by setting appropriate permissions with the X-Object-Sharing header. The permissions are applied using directory-based inheritance. A directory is an object with the corresponding content type. The default delimiter is /. Thus, each set of authorization directives is applied to all objects in the directory object where the corresponding X-Object-Sharing header is defined. If there are nested/overlapping permissions, the closest to the object is applied. When retrieving an object, the X-Object-Shared-By header reports where it gets its permissions from. If not present, the object is the actual source of authorization directives.

A user may GET another account or container. The result will include a limited reply, containing only the allowed containers or objects respectively. A top-level request with an authentication token, will return a list of allowed accounts, so the user can easily find out which other users share objects. The X-Object-Allowed-To header lists the actions allowed on an object, if it does not belong to the requesting user.

Shared objects that are also public do not expose the X-Object-Public meta information.

Objects that are marked as public, via the X-Object-Public meta, are also available at the corresponding URI returned for HEAD or GET. Requests for public objects do not need to include an X-Auth-Token. Pithos will ignore request parameters and only include the following headers in the reply (all X-Object-* meta is hidden):

Reply Header Name Value
ETag The ETag of the object
Content-Length The size of the data returned
Content-Type The MIME content type of the object
Content-Range The range of data included (only on a single range request)
Last-Modified The last object modification date (regardless of version)
Content-Encoding The encoding of the object (optional)
Content-Disposition The presentation style of the object (optional)

Public objects are not included and do not influence cross-user listings. They are, however, readable by all users.

Summary

List of differences from the OOS API:

  • Support for X-Account-Meta-* style headers at the account level. Use POST to update.
  • Support for X-Container-Meta-* style headers at the container level. Can be set when creating via PUT. Use POST to update.
  • Header X-Container-Object-Meta at the container level and parameter meta in container listings. (TBD)
  • Account and container policies to manage behavior and limits. Container behavior overrides account settings. Account quota sets the maximum bytes limit, regardless of container values.
  • Headers X-Container-Block-* at the container level, exposing the underlying storage characteristics.
  • All metadata replies, at all levels, include latest modification information.
  • At all levels, a HEAD or GET request may use If-Modified-Since and If-Unmodified-Since headers.
  • Container/object lists include more fields if the reply is of type JSON/XML. Some names are kept to their OOS API equivalents for compatibility.
  • Option to include only shared containers/objects in listings.
  • Object metadata allowed, in addition to X-Object-Meta-*: Content-Encoding, Content-Disposition, X-Object-Manifest. These are all replaced with every update operation, except if using the update parameter (in which case individual keys can also be deleted). Deleting meta by providing empty values also works when copying/moving an object.
  • Multi-range object GET support as outlined in RFC2616.
  • Object hashmap retrieval through GET and the format parameter.
  • Object create via hashmap through PUT and the format parameter.
  • The object’s Merkle hash is always returned in the X-Object-Hash header.
  • The object’s UUID is always returned in the X-Object-UUID header. The UUID remains unchanged, even when the object’s data or metadata changes, or the object is moved to another path (is renamed). A new UUID is assigned when creating or copying an object.
  • Object create using POST to support standard HTML forms.
  • Partial object updates through POST, using the Content-Length, Content-Type, Content-Range and Transfer-Encoding headers. Use another object’s data to update with X-Source-Object and X-Source-Version. Truncate with X-Object-Bytes.
  • Include new version identifier in replies for object replace/change requests.
  • Object MOVE support and ignore_content_type parameter in both COPY and MOVE.
  • Conditional object create/update operations, using If-Match and If-None-Match headers.
  • Time-variant account/container listings via the until parameter.
  • Object versions - parameter version in HEAD/GET (list versions with GET), X-Object-Version-* meta in replies, X-Source-Version in PUT/COPY.
  • Sharing/publishing with X-Object-Sharing, X-Object-Public at the object level. Cross-user operations are allowed - controlled by sharing directives. Available actions in cross-user requests are reported with X-Object-Allowed-To. Permissions may include groups defined with X-Account-Group-* at the account level. These apply to the object - not its versions.
  • Support for directory-based inheritance when enforcing permissions. Parent object carrying the authorization directives is reported in X-Object-Shared-By.
  • Copy and move between accounts with X-Source-Account and Destination-Account headers.
  • Large object support with X-Object-Manifest.
  • Trace the user that created/modified an object with X-Object-Modified-By.
  • Purge container/object history with the until parameter in DELETE.
  • Bulk COPY/MOVE/DELETE objects starting with prefix

Clarifications/suggestions:

  • All non-ASCII characters in headers should be URL-encoded.
  • Authentication is done by another system. The token is used in the same way, but it is obtained differently. The top level GET request is kept compatible with the OOS API and allows for guest/testing operations.
  • Some processing is done in the variable part of all X-*-Meta-* headers. If it includes underscores, they will be converted to dashes and the first letter of all intra-dash strings will be capitalized.
  • A GET reply for a level will include all headers of the corresponding HEAD request.
  • To avoid conflicts between objects and virtual directory markers in container listings, it is recommended that object names do not end with the delimiter used.
  • The Accept header may be used in requests instead of the format parameter to specify the desired request/reply format. The parameter overrides the header.
  • Container/object lists use a 200 return code if the reply is of type JSON/XML. The reply will include an empty JSON/XML.
  • In headers, dates are formatted according to RFC 1123. In extended information listings, the last_modified field is formatted according to ISO 8601 (for OOS API compatibility). All other fields (Pithos extensions) use integer tiemstamps.
  • The Last-Modified header value always reflects the actual latest change timestamp, regardless of time control parameters and version requests. Time precondition checks with If-Modified-Since and If-Unmodified-Since headers are applied to this value.
  • A copy/move using PUT/COPY/MOVE will always update metadata, keeping all old values except the ones redefined in the request headers.
  • A HEAD or GET for an X-Object-Manifest object, will include modified Content-Length and ETag headers, according to the characteristics of the objects under the specified prefix. The Etag will be the MD5 hash of the corresponding ETags concatenated. In extended container listings there is no metadata processing.

Table Of Contents

Previous topic

Cyclades/Image API Guide

This Page

Navigation

© Copyright 2012-2013, GRNET. Created using Sphinx 1.1.3.